1. Field of the Invention
The present invention relates to a beam irradiation apparatus which is suitably used in an inter-vehicle distance detector, a distance detector, and the like.
2. Description of the Related Art
In recent years, detection apparatuses which irradiate laser light to a target region to detect an obstacle within the target region are mounted on household passenger automobiles and the like. In such detection apparatuses, the presence or absence of the obstacle within the target region and a distance to the obstacle is detected based on the conditions of reflected light in irradiating laser light to the target region.
Here, irradiation of the laser light to the target region is ordinarily performed by a beam irradiation apparatus located in the detection apparatus. The beam irradiation apparatus includes an actuator using a polygon mirror and a lens actuator as a configuration for scanning the laser light within the target region.
In Japanese Patent Publication Laid-Open No. 11-83988, there is introduced a mechanism of scanning by a lens actuator. In accordance with this scanning mechanism, the laser light is scanned within the target region by driving a lens in two-dimensional directions. In this case, by appropriately adjusting a driving current applied to the actuator, a position within the target region to which the laser light is irradiated can be freely changed. Therefore, a scanning pattern of the laser light can be freely established.
However, in the scanning mechanism using a lens actuator, there is a possibility that the error in a relationship between the driving current and a shift amount of a lens (a position of laser light-irradiation) may be produced due to secular changes or the like. In this case, even if a prescribed driving current is applied to the actuator, the laser light is irradiated to a position deviated from a target position.